The invention relates to a method for operating a display device of a motor vehicle, by which image content on a screen. The invention also includes a display device of a motor vehicle.
In a motor vehicle, provision may be made for a list of function names to be displayed to a user on a screen of a display device, from which the user can choose in order to activate the named function. The display device may be part of a combination instrument or an infotainment system, for example. The user must then be able to move a cursor, for example, over the list elements in order to mark the desired function. Provision may similarly be made for the user to shift the list elements in the displayed list in such a manner that the desired list entry is at the very top, for example, and is activated hereby when a confirmation key is actuated. In order to move the cursor or shift the list contents, a rotary actuator or a rocker switch, for example, may be provided to the user in the motor vehicle as an operating element. Such operating elements generally cannot be used to produce continuous signals. The dial of a rotary actuator may therefore have latching positions. If the latching position changes, this is detected by an encoder of the rotary actuator in intervals of 30 ms to 60 ms, for example, and an electrical signal pulse is then generated, which pulse indicates the direction of rotation and signals the number of latching positions by which the dial has been shifted since the last detection. Such a signal pulse is also referred to as a tick.
When the operating element is actuated, a cursor, for example, is nevertheless not shifted on the screen suddenly with each received signal pulse but rather in a sliding movement. For this purpose, memory content of a target position memory is changed in the display device on the basis of the signal pulses and the sliding scrolling is then shifted to the target position in a plurality of steps of shifting the image content on the screen. This technique is also referred to as “scrolling”. The screen display is updated during scrolling at an image refresh rate which may be 60 Hz or 120 Hz, for example, and therefore allows flowing movements to be represented.
If the user generates a plurality of signal pulses by actuating the operating element, the memory content is successively updated as a result. The sliding scrolling is carried out in the meantime. After the user has then stopped rotating the dial, the target position has by no means been reached. Undesirably long running-on of the shifting operation on the screen may therefore result. If the user also changes the direction of rotation of the dial in this case during actuation, the situation may occur in which the cursor is first of all shifted in the one direction for a while and only then changes its movement direction, whereas the user has already stopped rotating the dial. In this case, the movement of the image content on the screen loses the relationship to the actual operating action.
An animation acceleration method may therefore be provided for such animations. This is explained below using FIG. 1.
FIG. 1 indicates by way of example, on a time axis along the time t (here indicated in seconds), when signal pulses P1 to P9 are generated by an operating element, for example a rotary actuator, and arrive at a control device of a display device of a motor vehicle. At the normal actuation speed, a pulse amplitude of these ticks is one. In this case, a tick with the pulse amplitude of one shifts image content, for example a cursor, by a particular shifting distance, for example 5 pixels or 10 pixels, on the screen of the display device. In the graph in FIG. 1, this applies to the signal pulses P1 to P5 and P9. The signal pulses P6 to P8 have larger pulse amplitudes since the user has adjusted the operating element with a faster movement in this case. The shifting of the image content must accordingly be greater. The graph in FIG. 1 also indicates the memory content Z of the target position memory mentioned. It is changed with the arrival of each pulse P1 to P9. The time grid in which the memory content Z is plotted against the time in FIG. 1 corresponds to that stipulated by the image refresh rate of the display device.
At a time t=0, an actual position I of the image content on the screen corresponds to the target position predefined by the memory content Z. A difference D between the memory content Z and the actual position I results with the arrival of a signal pulse. The image content is then moved at a constant speed to the target position Z in a sliding scrolling movement. The step size of each shifting step when updating the screen content is initially a basic step size on which the shifting is based until the arrival of the signal pulse P6. For this reason, a linear curve profile of the actual position I results until the time t=0.3 seconds at which the actual position corresponds to the target position again. The step size was determined by a scrolling speed for each image refresh (the graph with the solid line in FIG. 1). With the arrival of the signal pulses P5 and P6, the difference D exceeds a threshold value which may be 2 in this case, for example. For this reason, the scrolling speed is increased after the arrival of the signal pulse P5. The image content is therefore shifted in greater shifting steps for each new image structure. As a result, the difference D undershoots the threshold value again between the arrival of the signal pulses P6 and P7. The scrolling speed is then reduced to 1 again (t=0.55 s). The signal pulse P7 then arrives, with the result that the difference D is above the threshold value again and the scrolling speed is set to the value 3 again. The user perceives this change in the scrolling speed as an unsettled, jumpy movement of the image content on the screen.